Goss Grains Research Articles

Texture Selection by Secondary Recrystallization in Grain Oriented Silicon Iron: Competitive Texture Components for Goss Grains

Texture Selection by Secondary Recrystallization in Grain Oriented Silicon Iron: Competitive Texture Components for Goss Grains

Preferential Growth of Secondary Recrystallized Goss Grains During Secondary Recrystallization Annealing in Grain Oriented Silicon Steel Sheet

Computer color mapping of the primary and secondary recrystallized Goss grains which formed during secondary recrystallization annealing was performed with an image analyzer, using crystallographic orientation data measured by a Kossel examination.The preferential growth of secondary recrystallized Goss grains took place in a defined zone at the 1/10 depth beneath the surface of the as-decarburized and primary recrystallized steel sheet.With short-time secondary recrystallization annealing, a secondary recrystallized Goss grain with an 80 × 50 μ m elliptical form grew preferentially in its defined zone.With further secondary recrystallization annealing, four secondary recrystallized Goss grains coalesced to sizes of 100-350 μ m, and exhibited a zigag morphology due to a difference in the degree of consumption of primary recrystallized grains by the secondary recrystallized Goss grains. Primary recrystallized grains with {100} , {100} , and {100} orientations were resistant to comsumption by secondary recrystallized Goss grains, but those with {110} and {111} orientations were easily consumed by secondary recrystallized Goss grains.With long-time secondary recrystallized annealing, the full thickness of the silicon steel sheet was occupied by giant secondary recrystallized Goss grains, which ultimately extended to lengths of several millimeters. The orientation of the secondary recrystallized Goss grains is highly aligned to the [001] axis rather than the (110) crystallographic plane.It is considered that the nuclei for preferentially developing secondary recrystallized grains are inherited by the structure memory from highly oriented (110)[001] areas at the 1/10 depth beneath the surface of hot-rolled silicon steel sheet.

The role of special grain boundaries during the grain growth in Fe-3%Si

An experimental study of the role of coincidence site lattice (CSL) boundaries in the process of grain growth in grain oriented Fe-3%Si has provided important information about the development of texture. Specimens obtained after decarburization were annealed at temperatures both lower and higher than the temperature of secondary recrystallization. The textures of these specimens were analyzed and the frequency of CSL boundaries from all grains was calculated. In addition, the frequency of CSL boundaries with respect to the 110 〈001〉 grains was calculated for the investigated specimens. By comparing the distribution of CSL boundaries obtained for Goss grains and the distribution of CSL boundaries from all grains, it was possible to predict which CSL boundaries affect the Goss grain growth during secondary recrystallization. Our analysis indicates that Goss grains having a high amount of Σ5 CSL boundaries before the secondary recrystallization have a lower number of these boundaries during grain growth. Analysis of other types of grain boundaries indicate that development of the 110 〈001〉 texture in silicon steel is not influenced by the total number of CSL boundaries, but rather by the frequency of specific CSL boundaries such as the Σ5 CSL boundaries. In the investigated specimens, the Goss grains have a size advantage over other grains, which can be considered another important factor in the preferred growth of Goss grains.

TiN被覆した超低鉄損一方向性珪素鋼板の磁区細分化

In order to clarify the mechanism responsible for the ultra-low iron loss in TiN-coated grain oriented silicon steel sheet, direct observations were made of the domain structure obtained by coating a thin TiN film, which had been produced by ion plating on polished silicon steel sheets.The results obtained are summarized as follows.(1) After making distinct chemically polished and TiN-coated areas inside a single giant secondary Goss grain of a silicon steel sheet, the domain structure of the chemically polished area showed an original main domain with large black and white 180° domain wall spacings elongated in the rolling direction, while that of the TiN-coated area showed marked domain refinement due to the induced strong tensile stress by the TiN film.(2) At the borderline between the chemically polished area and the TiN-coated area, the domain wall spacings changed drastically, showing four to six narrow wall spacings in the coated area for each wall spacing in the polished area, and lens-like refined-domains also formed at the beginning of the TiN coating area from the large black and white 180° main domains.(3) In the chemically polished side of these line between the two areas, longitudinally striped domains formed distinctively within regions about ±45° to the rolling direction due to local strain arising from the strong surface tension in the TiN film.(4) By causing a slight deviation in the orientation of the secondary Goss grains in the silicon steel sheet, both the main domain and its refined domain in the chemically polished and TiN-coated area became less pronounced.(5) It is considered that the ultra-low iron loss in TiN-coated silicon steel sheet was obtained due to the reduced eddy current loss arising from the strong surface tension of the TiN coating on the silicon steel sheet, which induced radical domain refinement.

A general theory of secondary recrystallization in grain oriented Fe-Si: Metallurgical parameters controlling the microstructural evolution

The secondary recrystallization (SR) process and the related effects on the magnetic properties of silicon-iron are discussed in the framework of the general statistical theory of grain growth including texture and Zener drag influence. It has been shown that SR in silicon-iron is related to a selective growth process experienced by Goss grains due to specific grain boundary conditions generated by the surrounding grains (texture). In this paper some examples showing the specific role of various microstructural parameters influencing the selectivity of SR (such as Zener drag intensity and its drop rate, initial grain size, etc.), are discussed and related to the magnetic properties, which are mainly controlled by the final average grain size and orientation.

Goss grains originating from mid-thickness in single-staged high-permeability electrical steel

A study has been made of effects on secondary recrystallization of a high permeability steel of reducing the gauge, chemically, immediately before final texture annealing. The results indicate that although the proportion of Goss nuclei may be higher near the surface, nuclei capable of producing excellent final texture exist at least to levels 30% of the strip thickness below the surface. In addition, data and comments are included on interactions between the anneal atmosphere and strip surface, and their role in the selection of the Goss nuclei for growth in both HGO and RGO.

一方向性珪素鋼板の2次再結晶初期のGoss方位粒の優先成長

Computer color mapping for the preferential growth of secondary recrystallized Goss grains at an incipient stage during secondary recrystallization in the grain oriented silicon steel sheet was performed with an image analyzer, using crystallographic orientation data measured by a Kossel examination.The results are summarized as follows.(1) With secondary recrystallization annealing for 3 h at 850°C, secondary recrystallized Goss grain in an ellipitcal form of 80 μm in the rolling direction and 50 μm in the transverse direction grew preferentially at 1/10 depth beneath the surface of the silicon steel sheet.(2) With secondary recrystallization annealing for 7 h at 850°C, four secondary Goss grains coalesced to 100-350 mm in size grew preferentially in a state elongated in the rolling direction.(3) The deviation angle of orientation of these coalesced secondary Goss grains was within 2 degrees.(4) It is considered that the preferential growth of secondary recrystallized Goss grains at an incipient stage of secondary recrystallization annealing took place in the defined zones at 1/10 depth beneath the steel surface, these zones being inherited by the structure memory near the surface of the hot-rolled silicon steel sheet.

Caractérisation de la texture de recristallisation primaire et de la spécialité des joints de grains de tôles de Fe-3%Si par diffraction des electrons rétrodiffusés

The EBSP (electron backscattering pattern) technique has been used to verify and to complete a study by Rouag [Thèse de Doctorat d'Etat (1988), University de Paris Sud, Orsay, France] concerning the influence of crystallographic texture and grain boundaries during abnormal growth of Goss grains in Fe-3%Si sheets, grade Hi-B. 1000 individual orientations have been measured at three levels: at the surface, at a fifth of the thickness from the surface and at the middle of the sheet. This technique allows the calculation of a true orientation distribution function (ODF), which is not possible using X-ray (or neutron) diffraction. Indeed, for X-ray diffraction, only the even part of the ODF can be determined. For the even part of the ODF, the results obtained by EBSPs are in good agreement with those obtained by X-ray diffraction and show the importance of the contribution of the odd part (about 20% of the true ODF). Then the minimal value of the orientation number is determined to assess an ODF statistic. This short study shows that it is useful to determine a minimum of 1000 measurements at each level. From these 3000 measurements, the nature of the grain boundaries is determined showing a good agreement with results obtained in the literature. In particular, it appears that the percentage of coincidence site lattice (CSL) boundaries, which is about 10%, does not depend on the sampling position. Moreover, another short study of the influence of orientation number on the nature of grain boundaries shows that a good representation is obtained if about 750 measurements are taken into account.

Configuration of Primary Recrystallized Grains Resistant to Consumption by Secondary Recrystallized Goss Grains

Computer color mapping of the primary recrystallized grains near the growing front of secondary recrystallized Goss grains was performed with an image analyser, using crystallographic orientation data measured by a Kossel examination. (1) The {100} - primary recrystallized grains were virtually unconsumed by secondary recrystallized Goss grains. It was consistent with the results of previous experiments. (2) The primary recrystallized grains of alternate configuration with two equivalent orientations of near (342) [430] and (342) [430] were also virtually unconsumed by secondary recrystallized Goss grains

AlNとMnSを含んだFe-3%Siの{110}⟨111⟩方位2次再結晶粒の成長

A primary recrystallized specimen having few grains with Goss orientation was made by Taguti’s method through increasing cold rolling reduction and it was then annealed in a 100%N2 or 100%H2 atmosphere.The {110}〈111〉 secondary recrystallization was evolved and no {110}〈001〉 secondary grains were made when annealed in a 100%N2 atmosphere. Normal grain growth with a major orientation of {113}〈14 23 3〉 occurred when annealed in a 100%H2 atmosphere.The mechanism of the evolution of {110}〈111〉 secondary recrystallization can be considered to be due to the relatively higher intensity of the nucleus compared with that of {110}〈001〉 and the second highest frequency of gains in Σ9 orientation relationship compared with that of a Goss grain in the primary matrix. The mechanism of the evolution of normal grain growth with a {113}〈14 23 3〉 major orientation may be due to the selective grain growth of the surface layer of the primary recrystallized specimen caused by a decrease in the inhibition effect of AlN precipitates in the surface layer, which has {113}〈14 23 3〉 as the major orientation.

Goss方位2次再結晶粒に蚕食されにくい1次再結晶粒の配列

Goss方位2次再結晶粒に蚕食されにくい1次再結晶粒の配列

Evolution of local texture and grain boundary characteristics during secondary recrystallisation of Fe-3% Si sheets

A study of the evolution of the local texture has shown that the migration rate of special boundaries is higher than that of general boundaries in a polycrystalline materials. The results of the evolution of the local texture are consistent with those related to the anisotropy of grain boundaries migration velocity surrounding the growing Goss grain. Furthermore, it has been taken i nto consideration that, on an average, all grains having an orientation relationship corresponding to that of a special boundary with the Goss grain have the same “texture” effect relative to its growth; these grains have been considered as a texture component belonging to orientations present in the sheet. The amount of grains belonging to this component is much more important than that of the Goss component and their mean grain size is higher than that of {110} 〈001〉 grains: results point out that grain boundaries between these two “components” of texture have a very high diffusivity. In these conditions, the growth model developed by Abbruzzese and Lucke predicts a high growth rate of a small amount of Goss grains to the detriment of the other component: this mode of growth corresponds well to the case of secondary recrystallisation.

一方向性珪素鋼板のGoss 2次再結晶形成メカニズム

Mechanism of secondary recrystallization in grain oriented silicon steel processed both with one-stage and two-stage cold rolling methods has been investigated using materials containing MnS alone or MnS and AlN as inhibitors.(1) In the one-stage cold rolling method, the Goss orientation has the specifically high intensity of Σ9 orientations in a primary recrystallized matrix. When AlN and MnS are used as inhibitors, the Goss orientation grows preferentially consuming grains with Σ9 orientation while other grains remain inhibited resulting in the Goss secondary recrystallization.When only MnS is used as an inhibitor, no secondary recrystallization occurred due to the poor inhibitor effect of MnS.(2) In the two-stage cold rolling method, the Goss secondary recrystallization evolves regardless of the inhibitors used. The required intensity level of the inhibitors for the secondary recrystallization in the two-stage cold rolling method is relatively low compared with that of the one-stage cold rolling method.The intensity of Σ9 orientation in relation to the Goss orientation is not the highest among other orientations, but the intensity of the Goss orientation itself has a peak value in a primary recrystallized matrix. Therefore, the PCNΣ9 value, a product of the intensity of Goss orientation and the intensity of Σ9 orientation in the primary matrix, is the highest except for the orientations having very high intensity of Σ1 orientations. The occurrence of the Goss secondary recrystallization in the two-stage cold rolling method is considered to be determined by the PCNΣ9 value as this value is associated with a probability of a Goss grain coming into contact with a grains of Σ9 orientation.

Al-ギルド鋼の1次再結晶集合組織と2次再結晶方位の関係

In attempt to clarify the mechanism of secondary recrystallization in aluminum killed steel, the orientation relationship between the secondary Goss grains and primary recrystallization texture was investigated by analysis of X-ray pole figure measurement. The main results obtained are as follows.(1) In 70% cold rolling reduction, the intensity of the Goss orientation is high in the primary recrystallization stage and the evolution of Goss texture is considered to be originated in the higher PCNΣ9 value, a product of the intensity of Goss orientation and the intensity of Σ9 orientation in relation to the Goss orientation (ICΣ9 value) in the primary matrix.(2) In 85% cold rolling reduction, the intensity of the Goss orientation in the primary matrix is lower, but the Goss orientation has a higher intensity of Σ9 orientations than any other orientations in the primary matrix. Therefore, the occurrence of the Goss secondary grains in this case is considered to be due to the higher ICΣ9 value.

Development of Goss texture during grain growth in Fe-3% Si

In order to study the development of the Goss grain size distribution during grain growth, a 3% silicon-iron industrial material was investigated by different metallographic technics (X-ray analysis, etch-pitting), after decarburization and just before secondary recrystallization.The results show as the special conditions of texture and inhibition allow Goss grains ({110} ⟨001⟩) to grow much faster than all other grains. This grain selection is the process which leads to an abnormal grain growth (secondary recrystallization).A computer simulation based on the selective growth mechanism produces results in perfect agreement with the experimental ones.

Influence of Grain Boundary Characteristics and of Chemical Parameters on Abnormal Grain Growth in Fe–3% Si Sheets

The purpose of the present study was to precise mechanisms at the origin of the exaggerated Goss grain growth of Fe–3% Si sheets, grade Hi–B. It has been pointed out that at the primary recrystallized state, the Goss grains which belong to the small grain class are present through the whole sheet thickness. In presence of AlN and MnS inhibitors, their growth during the anisothermal secondary recrystallization annealing is due to the high mobility of the special C.S.L. boundaries; their subsequent expanse at the fifth of the sheet thickness is favoured by purification of the sheet. Indeed, after dissociation of AlN and MnS precipitates at high temperature, a concentration gradient in sulfur and in nitrogen due to the reducing hydrogen atmosphere has been observed in subsurface thanks to SIMS experiments, such as general and C.S.L. boundaries can easily move whereas those at the center of the sheet are more dragged.

3%Si-Fe合金の1次再結晶板の{110}方位粒分布と2次再結晶粒方位の関係

In an attempt to clarify the mechanism of secondary recrystallization in 3%Si-Fe, the orientation relationship between the secondary Goss grains and the matrix texture and the Goss nucleus in the primary texture was investigated utillizing X-ray (vector method) and SEM-ECC-ECP technique. The main results obtained are as follows.(1) The largest grain present in the surface of primary recrystallized specimen was not a Goss oriented grain and the frequency peak of Goss oriented grains deviated about 0.035 rad from the rolling direction when processed by the one-stage cold rolling method. The intensity peak of Goss grains was situated within 0.087 rad from the rolling direction when processed by the two-stage cold rolling method.(2) The frequency distribution of Σ9 coincidence grains corresponding to Goss grains rotated about ND axis has a peak value at an ideal Goss orientation in the primary matrix processed by the one-stage cold rolling method, while no peak value was recognized at the ideal Goss orientation when processed by the two-stage cold rolling method.(3) The frequency distribution of Goss secondaries has a peak value at an ideal Goss orientation. However, in the two-stage cold rolling process, a peak value is situated between 0.09 and 0.18 rad apart from an ideal Goss orientation.(4) It can be concluded from the above findings that the distribution of coincidence boundaries rather than the size and the frequency of Goss grains in the primary texture mainly determines the sharpness of Goss secondaries in the grain oriented silicon steel processed both by the one- and two-stage cold rolling methods.

Computer color mapping of configuration of goss grains after an intermediate annealing in grain oriented silicon steel.

In order to elucidate the formation of Goss grains after an intermediate annealing in grain oriented silicon steel, computer color mapping was performed by processing the orientation information of Kossel diffraction patterns taken from the recrystallized grains in advance.The Goss grains forming colonies in the vicinity of steel surface after an intermediate annealing occupy an extremely large area inside the defined {hk0} matrix bands. The size of each Goss grain in this region is comparable to or slightly larger than that of other matrix grains. The perfection o f the [001] alignment o f the colonized Goss grains is much better than that of (110) plane and the colonized Goss grains are formed with the small boundary width of within 10° in the crystallographic plane. It is considered that the formation areas of Goss grains inherited by the structure memory from the original hot rolled texture take place with the strong perfection of the [001] alignment inside the defined {hk0} matrix bands.

Computer color mapping of configuration of Goss grains after transverse cold rolling in grain oriented silicon steel.

Computer color mapping of configuration of Goss grains after transverse cold rolling in grain oriented silicon steel.

Origin and development of through-the-thickness variations of texture in the processing of grain-oriented silicon steel

In the production of high-permeability grain-oriented silicon steel, through-the-thickness variations of texture in the hot-rolled sheet make an important contribution to the perfection of secondary recrystallization. In particular, large grains at a depth of 20 to 25 Pct of the thickness are thought to provide the nuclei for secondary recrystallization. In this report, formation of the Goss orientation in the subsurface to intermediate layer of hot-rolled sheets has been studied by rolling with a variety of draft schedules and also by rolling in a high-speed laboratory mill equipped with a means for quenching at predetermined times as short as 10 msec after rolling. Formation of a texture gradient in the hot-rolled sheet is shown to be controlled by the sequence of deformation and recrystallization during rolling. The Goss grains are found to originate from a shear deformation of ferrite crystals due to the high friction in hot rolling and to grow by a coalescence process. The effects of through-the-thickness variations of the hot-rolling texture, together with the inhomogeneities originating from the history of partial phase transformation in the hot-rolling stage, are discussed in connection with optimal selection of the processing variables leading to the perfection of secondary recrystallization, in terms of the sites providing the source of potential nuclei and those preparing the favorable surroundings for an extensive growth of the viable nuclei in the final annealing.